HomeLab discussions, as a tool for learning & certifications are welcomed.

Braindump / Certification Cheating.

These topics pollute our industry and devalue the hard work of others.

These posts will be deleted without mercy.

Blogspam / Traffic Redirection.

This sub prefers to share knowledge within the sub community.

Directing our members to resources elsewhere is closely monitored.
-- You may announce the existence of your blog/YouTube Channel.
-- You may share a URL to a blog that answers questions already in discussion.
-- But harassing members to check out your content will not be tolerated.

Low-quality posts.

Any post that fails to display a minimal level of effort prior to asking for help is at risk of being Locked or Deleted.

We expect our members to treat each other as fellow professionals. Professionals research & troubleshoot before they ask others for help.

The bigger issue is not from existing switches but the lack of control when adding new switches. You can wipe the configuration from a switch which won't remove the vlan database nor the VTP version number. If the version of the new switch is higher it will overwrite everything in said domain. To compound that even if you null out the domain name VTP will learn the existing domain name and then realize it has a higher revision number and pump out it's vlan DB to everyone in the domain. Regardless of whether or not it's a client or a server. Remember: Clients can update servers without an issue.

There are other little things that cause issues such as trunks not coming up if there are VTP domain mismatches or version number mismatches (in transparent mode).

There are enough knobs and buttons in VTP that when things don't match up completely they'll either be irksome or catastrophic.

And again, considering the way network design has gone in more recent years, there isn't much of a need for it anyway. We've largely moved away from multi-tiered layer 2 topologiesvoidwhereprohibited,restrictionsmayapply,notallapplicantswillbeeligible. Thus rendering VTP irrelevant.

**tl;dr* the moral of the story is: It's not all that useful anymore and can cause more issues than not. 1/10 would not configure again.*

In my case a student took a configuration backup of the core switch for use in the lab, wiped all the VLANs (as you do) and then when it was reconnected to the network....it had a higher revision number.

It happens SO often. When I was an intern we were doing refreshes at stores for a smaller grocery chain where I went to school. There was 1 engineer and two of us intern grunts. we had configured a pair of the switch stacks already and gotten everything nicely set up. The other intern was in the back getting the fiber to another switch set up. None of us realized that switch had been used for some testing so it had some oddball VLANS on it, none of which we needed. So before we knew it... And a VTP configuration.

Yadda yadda yadda we had to reconfigure all of the VLANs for the whole store. The up side was the limited number of VLANs to reconfigure. The downside is we didn't realize this happened until well after we had finished configuring things... and troubleshooting the random connectivity issues.

Even on a L3 switch you need to create the VLAN in L2 before anything in L3 will work. This is a step newbies often miss, and experts sometimes miss, which is a little bit embarrassing when it happens.

But generally speaking, to get traffic from one VLAN to another you need a L3 device, this can be an L3 switch or a router. I guess you've already got something that can route between VLANs, as you've got three VLANs today.

You can use an L2 switch that provides VLAN access to devices (we'd call this the access layer in Cisco-speak) and this can connect to an L3 switch for routing between VLANs.